Tissue substitute materials and methods for tissue repair

ABSTRACT

Non-woven graft materials for use in specialized surgical procedures such as neurosurgical procedures, methods for making the non-woven graft materials, and methods for repairing tissue such as neurological tissue using the non-woven graft materials are disclosed. More particularly, disclosed are non-woven graft materials including at least two distinct fiber compositions composed of different polymeric materials, methods for making the non-woven graft materials and methods for repairing tissue in an individual in need thereof using the non-woven graft materials.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 15/152,726, filed May 12, 2016, now U.S. Pat. No. 10,632,228.Any and all applications for which a priority claim is identified hereor in the Application Data Sheet as filed with the present applicationare hereby incorporated by reference under 37 CFR 1.57.

BACKGROUND OF THE DISCLOSURE

The present disclosure relates generally to non-woven graft materialsfor use in specialized surgical procedures such as neurosurgicalprocedures, wound repair, oral surgery, dermal repair and regeneration,head and neck surgery, endonasal surgery and bone repair, methods formaking the non-woven graft materials, and methods for repairing tissuesuch as neurological tissue using the non-woven graft materials. Moreparticularly, the present disclosure relates to non-woven graftmaterials including at least two distinct fiber compositions composed ofdifferent polymeric materials, methods for making the non-woven graftmaterials and methods for repairing tissue in an individual in needthereof using the non-woven graft materials.

Neurosurgical procedures commonly result in the perforation or removalof the watertight fibrous membrane surrounding the brain known as thedura mater. In all of these cases, the tissue barrier surrounding thebrain must be repaired in a watertight manner in order to prevent damageto cortical tissues and leakage of cerebrospinal fluid. Dura substitutesare therefore needed to repair dural defects, reestablish the barrierthat encloses the cerebrospinal space, and prevent cerebrospinal fluid(CSP) leakage and infection.

Numerous materials are currently in use as dura substitutes, includingautograft, allograft, xenograft, and non-biologic synthetic materials.An ideal dura substitute should adequately restore the continuity of thedura mater and prevent CSP leak while minimizing infection. Themechanical properties of the material should facilitate suturing and/ortacking, yet also mimic the compliance of natural dura to allow ease ofdraping over delicate cortical tissues. Furthermore, an ideal durasubstitute will minimize local tissue inflammation and preferablyencourage the infiltration of cells and vasculature to expedite thereconstruction of native dura without inducing undesired outcomes offibrosis or cortical adhesions.

Autograft materials utilized in dura repair are commonly acquired from apatient's own pericranium or facia latae. These tissues are desirabledue to their minimal inflammatory response and their similarity tonative dura. However, the use of these grafts is limited by the pooravailability and host-site morbidity of the autograft material.Alternatively, human tissue is commonly utilized in the form ofallografts, which are obtained from cadaveric dura. This tissue can becollected, sterilized, and stored to provide greater availability ofgraft material to repair large dura defects. However, significant riskof disease transmission limits the use of allografts in contemporaryneurosurgical settings.

Xenograft materials are also commonly utilized as dura substituteproducts. Xenogenic materials are derived from bovine or porcine sourcesand are available in the form of decellularized tissues of thepericardium, small intestinal submucosa, and dermis or in the form ofprocessed materials synthesized from collagen-rich sources such as thebovine Achilles tendon. Like allografts, xenografts have an inherentrisk of zoonotic disease transmission and the potential to inciteallergic and inflammatory reactions. Many biologic grafts have theadvantage of being fully remodeled, whereby the natural components ofthe graft (e.g. collagen) recruit cell infiltration and angiogenesisthat participate in the restructuring of the graft material. However,the rate at which a biologic graft is remodeled and resorbed is not wellcontrolled, such that graft degradation can occur prematurely. Thismismatch between graft resorption and native tissue regeneration canresult in thin, weak tissue in the dura defect. The mechanicalproperties of xenograft materials also vary greatly due to differencesin material processing such as crosslinking and protein denaturation.Select products have limited mechanical strength as to only be suitablefor use as only grafts without the option of suturing. Other xenograftmaterials, however, provide the tear resistance and tensile strengthrequired for suturing.

Some bovine-derived collagen materials are crosslinked to provide themechanical strength necessary for suture repair of a dural defect. Thismanipulation of the mechanical properties can result in undesirableeffects in the handling of the material, leading to a dura substitutewith decreased compliance. Furthermore, the crosslinking of thebovine-derived collagen material has been shown to interfere with thedegradation expected of its biologic collagen composition, leading toprolonged presence at the implant site with poorly defined materialresorption. For biologically derived dura substitutes, desirablemechanical properties for suturability and desirable resorptionproperties for tissue remodeling are often mutually exclusive.

Despite the range of existing dura substitute materials available incontemporary neurosurgical clinics, there remains a need for a durasubstitute that offers improved handling characteristics, mechanicalproperties, and safety compared to biologically derived grafts.Non-biologic synthetic materials have been explored to overcome thelimitations of biologic grafts, whereby material strength, resorption,and safety can be controlled with much greater precision. Despite theseofferings, tissue response to synthetic grafts has yet to be fullyexplored. Synthetic grafts also fall short in their approximation of themechanical properties of the dura mater, such that these materials oftenhave poor handling that complicates their clinical use.

Based on the shortcomings of the current clinically available materials,there remains a need for an improved resorbable non-biologic durasubstitute that provides better handling and ease of use and improvesthe local tissue response during reconstruction of the native dura.

BRIEF DESCRIPTION OF THE DISCLOSURE

The present disclosure relates generally to non-woven graft materials,methods for making the materials, and methods for repairing neurologicaltissue such as dura mater using the materials.

In one aspect, the present disclosure is directed to a resorbablenon-woven graft material comprising: a first non-woven fiber compositioncomprising poly(lactic-co-glycolic acid) and a second non-woven fibercomposition comprising polydioxanone.

In another aspect, the present disclosure is directed to a resorbablenon-woven graft material comprising: a first non-woven fibercomposition, wherein the first fiber composition comprises a polymerselected from the group consisting of polycaprolactone, polydioxanone,poly (glycolic acid), poly(L-lactic acid), poly(lactide-co-glycolide),poly(L-lactide), poly(D,L-lactide), poly(ethylene glycol),montmorillonite, poly(L-lactide-co-ε-caprolactone),poly(ε-caprolactone-co-ethyl ethylene phosphate),poly[bis(p-methylphenoxy) phosphazene],poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(ester urethane) urea,poly(p-dioxanone), polyurethane, polyethylene terephthalate,poly(ethylene-co-vinylacetate), poly(ethylene oxide), poly(phosphazene),poly(ethylene-co-vinyl alcohol), polymer nanoclay nanocomposites,poly(ethylenimine), poly(ethyleneoxide), poly vinylpyrrolidone,polystyrene (PS) and combinations thereof; and a second non-woven fibercomposition, wherein the second fiber composition comprises a polymerselected from the group consisting of polycaprolactone, polydioxanone,poly (glycolic acid), poly(L-lactic acid), poly(lactide-co-glycolide),poly(L-lactide), poly(D,L-lactide), poly(ethylene glycol),montmorillonite, poly(L-lactide-co-ε-caprolactone),poly(ε-caprolactone-co-ethyl ethylene phosphate),poly[bis(p-methylphenoxy) phosphazene],poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(ester urethane) urea,poly(p-dioxanone), polyurethane, polyethylene terephthalate,poly(ethylene-co-vinylacetate), poly(ethylene oxide), poly(phosphazene),poly(ethylene-co-vinyl alcohol), polymer nanoclay nanocomposites,poly(ethylenimine), poly(ethyleneoxide), poly vinylpyrrolidone;polystyrene and combinations thereof; and wherein the first fibercomposition and the second fiber composition comprise differentpolymers.

In another aspect, the present disclosure is directed to a method forpreparing a non-woven graft material, the method comprising: contactinga first fiber composition, wherein the first fiber composition comprisesa polymer selected from the group consisting of polycaprolactone,polydioxanone, poly (glycolic acid), poly(L-lactic acid),poly(lactide-co-glycolide), poly(L-lactide), poly(D,L-lactide),poly(ethylene glycol), montmorillonite,poly(L-lactide-co-ε-caprolactone), poly(ε-caprolactone-co-ethyl ethylenephosphate), poly[bis(p-methylphenoxy) phosphazene],poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(ester urethane) urea,poly(p-dioxanone), polyurethane, polyethylene terephthalate,poly(ethylene-co-vinylacetate), poly(ethylene oxide), poly(phosphazene),poly(ethylene-co-vinyl alcohol), polymer nanoclay nanocomposites,poly(ethylenimine), poly(ethyleneoxide), poly vinylpyrrolidone,polystyrene (PS) and combinations thereof; and a second fibercomposition, wherein the second fiber composition comprises a polymerselected from the group consisting of polycaprolactone, polydioxanone,poly (glycolic acid), poly(L-lactic acid), poly(lactide-co-glycolide),poly(L-lactide), poly(D,L-lactide), poly(ethylene glycol),montmorillonite, poly(L-lactide-co-ε-caprolactone),poly(ε-caprolactone-co-ethyl ethylene phosphate),poly[bis(p-methylphenoxy) phosphazene],poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(ester urethane) urea,poly(p-dioxanone), polyurethane, polyethylene terephthalate,poly(ethylene-co-vinylacetate), poly(ethylene oxide), poly(phosphazene),poly(ethylene-co-vinyl alcohol), polymer nanoclay nanocomposites,poly(ethylenimine), poly(ethyleneoxide), poly vinylpyrrolidone,polystyrene (PS) and combinations thereof; to form a non-woven graftmaterial.

In accordance with the present disclosure, methods have been discoveredthat surprisingly allow for the repair of dura mater. The presentdisclosure has a broad and significant impact, as it allows formaterials the overcome the shortcomings of existing materials andfacilitates effective and reliable repair of native dura.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure will be better understood, and features, aspects andadvantages other than those set forth above will become apparent whenconsideration is given to the following detailed description thereof.Such detailed description makes reference to the following drawings,wherein:

FIG. 1 is a scanning electron micrograph depicting an image of anexemplary non-woven fiber composition of the present disclosure.

FIGS. 2A and 2B are photographic images depicting bilateral duraldefects repaired with a non-woven graft material of the presentdisclosure (FIG. 2A) and a collagen graft material (FIG. 2B).

FIGS. 3A-3D are micrographic images depicting Hematoxylin &Eosin-stained sections obtained from defects repaired with a non-wovengraft material of the present disclosure (FIGS. 3A & 3C) and a collagengraft material (FIGS. 3B & 3D) 4 weeks post-operatively.

FIG. 4 is a graph depicting the quantitative comparison of adhesions topia mater present in defect sites implanted with a non-woven graftmaterial (bar 1) of the present disclosure and a collagen graft material(bar 2).

FIG. 5 is a graph depicting neoduralization present in defect sitesimplanted with a non-woven graft material of the present disclosure(bar 1) of the present disclosure and a collagen graft material (bar 2).

FIG. 6 is a graph depicting burst strength testing of the non-wovengraft material (hydrated) of the present disclosure (bar 1) as comparedto a collagen-based graft material (bar 2).

FIG. 7 is a graph depicting adhesions of the non-woven graft material ofthe present disclosure (bar 1) to pia mater as compared to adhesions ofa collagen-based graft material (bar 2) to pia mater at 4 weekspost-operatively.

FIG. 8 is a graph depicting neoduralization to the non-woven graftmaterial of the present disclosure (bar 1) as compared toneoduralization to a collagen-based graft material (bar 2) at 4 weekspost-operatively.

DETAILED DESCRIPTION OF THE DISCLOSURE

While the disclosure is susceptible to various modifications andalternative forms, specific embodiments thereof have been shown by wayof example in the drawings and are herein described below in detail. Itshould be understood, however, that the description of specificembodiments is not intended to limit the disclosure to cover allmodifications, equivalents and alternatives falling within the scope ofthe disclosure as defined by the appended claims.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which the disclosure belongs. Although any methods andmaterials similar to or equivalent to those described herein can be usedin the practice or testing of the present disclosure, the preferredmethods and materials are described below.

Non-Woven Graft Materials of the Present Disclosure

Generally, the present disclosure is directed to non-woven graftmaterials including two or more distinct types of fiber compositions,each of which possesses independent mechanical, chemical and/orbiological properties. For example, in one embodiment, inclusion of onefiber composition can stabilize the resulting non-woven graft material,while the other fiber composition can improve stability, free-shrinkageproperties, mechanical properties, and resorption rate of the non-wovengraft material.

As used interchangeably herein, “non-woven graft material” and“non-woven graft fabric” refer to a material having a structure ofindividual fibers or threads which are interlaid, but not in anidentifiable manner as in a knitted fabric. Non-woven graft materialsand non-woven graft fabrics can be formed from many processes such asfor example, electrospinning processes, meltblowing processes,spunbonding processes, melt-spraying and bonded carded web processes.The basis weight of non-woven graft materials is usually expressed inounces of material per square yard (osy) or grams per square meter (gsm)and the fiber diameters are usually expressed in nanometers andmicrometers (microns). Suitable basis weight of non-woven graftmaterials of the present disclosure can range from about 50 gsm to about300 gsm. More suitably, basis weight of non-woven graft materials of thepresent disclosure can range from about 70 gsm to about 140 gsm. Thetensile strength of the non-woven graft material of the presentdisclosure can range from about 5 Newtons (N) to about 50 Newtons (N),including from about 1 N to about 10 N to about 15 N. The strength ofthe non-woven graft material of the present disclosure can also bedescribed in terms of suture pull-out strength, which refers to theforce at which a suture can be torn from the non-woven graft material.Suitable suture pull-out strength can range from about 1 N to about 5 N.

As used herein the term “microfibers” refers to small diameter fibershaving an average diameter not greater than 75 microns, for example,having an average diameter of from about 0.5 microns to about 50microns, or more particularly, microfibers having an average diameter offrom about 2 microns to about 40 microns. Another frequently usedexpression of fiber diameter is denier. The diameter of a polypropylenefiber given in microns, for example, may be converted to denier bysquaring, and multiplying the result by 0.00629, thus, a 15 micronpolypropylene fiber has a denier of about 1.42 (152×0.00629=1.415).

As used herein, the terms “nano-sized fibers” or “nanofibers” refer tovery small diameter fibers having an average diameter not greater than2000 nanometers, and suitably, not greater than 1500 nanometers (nm).Nanofibers are generally understood to have a fiber diameter range ofabout 10 to about 1500 nm, more specifically from about 10 to about 1000nm, more specifically still from about 20 to about 500 nm, and mostspecifically from about 20 to about 400 nm. Other exemplary rangesinclude from about 50 to about 500 nm, from about 100 to 500 nm, orabout 40 to about 200 nm.

As used herein the term “spunbonded fibers” refers to small diameterfibers which are formed by extruding molten thermoplastic material asfilaments from a plurality of fine, usually circular capillaries of aspinnerette with the diameter of the extruded filaments then beingrapidly reduced as by, for example, in U.S. Pat. No. 4,340,563 to Appelet al., and U.S. Pat. No. 3,692,618 to Dorschner et al., U.S. Pat. No.3,802,817 to Matsuki et al., U.S. Pat. Nos. 3,338,992 and 3,341,394 toKinney, U.S. Pat. Nos. 3,502,763 and 3,909,009 to Levy, and U.S. Pat.No. 3,542,615 to Dobo et al.

As used herein the term “meltblown fibers” refers to fibers formed byextruding a molten thermoplastic material through a plurality of fine,usually circular, die capillaries as molten threads or filaments intoconverging high velocity gas (e.g. air) streams which attenuate thefilaments of molten thermoplastic material to reduce their diameter,which may be to microfiber diameter. Thereafter, the meltblown fibersare carried by the high velocity gas stream and are deposited on acollecting surface to form randomly disbursed meltblown fibers. Such aprocess is disclosed, for example, in U.S. Pat. No. 3,849,241. Meltblownfibers are microfibers which may be continuous or discontinuous and aregenerally smaller than 10 microns in diameter.

As used herein, the term “electrospinning” refers to a technology whichproduces nano-sized fibers referred to as electrospun fibers from asolution using interactions between fluid dynamics and charged surfaces.In general, formation of the electrospun fiber involves providing asolution to an orifice in a body in electric communication with avoltage source, wherein electric forces assist in forming fine fibersthat are deposited on a surface that may be grounded or otherwise at alower voltage than the body. In electrospinning, a polymer solution ormelt provided from one or more needles, slots or other orifices ischarged to a high voltage relative to a collection grid. Electricalforces overcome surface tension and cause a fine jet of the polymersolution or melt to move towards the grounded or oppositely chargedcollection grid. The jet can splay into even finer fiber streams beforereaching the target and is collected as interconnected small fibers.Specifically, as the solvent is evaporating (in processes using asolvent), this liquid jet is stretched to many times it original lengthto produce continuous, ultrathin fibers of the polymer. The dried orsolidified fibers can have diameters of about 40 nm, or from about 10 toabout 100 nm, although 100 to 500 nm fibers are commonly observed.Various forms of electrospun nanofibers include branched nanofibers,tubes, ribbons and split nanofibers, nanofiber yarns, surface-coatednanofibers (e.g., with carbon, metals, etc.), nanofibers produced in avacuum, and so forth. The production of electrospun fibers isillustrated in many publication and patents, including, for example, P.W. Gibson et al., “Electrospun Fiber Mats: Transport Properties,” AIChEJournal, 45(1): 190-195 (January 1999), which is hereby incorporatedherein by reference.

As used herein, the term “type” such as when referring to “differenttypes of fibers” or “distinct types of fibers” refers to fibers having“a substantially different overall material composition” with measurablydifferent properties, outside of “average diameter” or other “size”differences. That is, two fibers can be of the same “type” as definedherein, yet have different “average diameters” or “average diameterranges.” Although fibers are of different “types” when they have asubstantially different overall material composition, they can stillhave one or more components in common. For example, electrospun fibersmade from a polymer blend with a first polymeric component present at alevel of at least 10 wt % would be considered a different fiber typerelative to electrospun fibers made from a polymer blend that wassubstantially free of the first polymeric component. Fibers of different“types” can also have a completely different content, each made of adifferent polymer for example, or one made from a polymer fiber and theother from a titania fiber, or a ceramic fiber and a titania fiber, andso on.

As used herein the term “polymer” generally includes but is not limitedto, homopolymers, copolymers, such as for example, block, graft, randomand alternating copolymers, terpolymers, etc. and blends andmodifications thereof. Furthermore, unless otherwise specificallylimited, the term “polymer” shall include all possible geometricalconfiguration of the material. These configurations include, but are notlimited to isotactic and atactic symmetries.

The non-woven graft materials of the present disclosure typicallyinclude at least two distinct types of fiber compositions, each of whichpossesses independent mechanical, chemical and/or biological properties.The fiber compositions are suitably made of synthetic resorbablepolymeric materials. As used herein, the term “resorbable polymericmaterial” refers to material formed from resorbable (also referred to as“bioabsorbable”) polymers; that is the polymers possess the property tobreak down when the material is exposed to conditions that are typicalof those present in a post-surgical site into degradation products thatcan be removed from the site within a period that roughly coincides withthe period of post-surgical healing. Such degradation products can beabsorbed into the body of the patient. The period of post-surgicalhealing is to be understood to be the period of time measured from theapplication of the non-woven graft material of the present disclosure tothe time that the post-surgical site is substantially healed. Thisperiod can range from a period of several days to several monthsdepending on the invasiveness of the surgical and the speed of healingof the particular individual. It is intended that the subject non-wovengraft material can be prepared so that the time required for resorptionof the non-woven graft material can be controlled to match the timenecessary for healing or tissue reformation and regeneration. Forexample, in some non-woven graft materials of the present disclosure,the fiber compositions are selected to degrade within a period of aboutone week, while in other non-woven graft materials, the compositions areselected to degrade within a period of three years, or even longer ifdesired.

The fiber compositions used in the present disclosure can be producedfrom any resorbable material that meets the criteria of that material asthose criteria are described above. The fiber compositions can be formedfrom resorbable polymers such as (but not limited to) polymers of lacticand glycolic acids, copolymers of lactic and glycolic acids,poly(ether-co-esters), poly(hydroxybutyrate), polycaprolactone,copolymers of lactic acid and ε-aminocapronic acid, lactide polymers,copolymers of poly(hydroxybutyrate) and 3-hydroxyvalerate, polyesters ofsuccinic acid, poly(N-acetyl-D-glucosamine), polydioxanone, cross-linkedhyaluronic acid, cross-linked collagen, and the like, and combinationsthereof. Suitable synthetic polymers can be, for example,polycaprolactone (poly(ε-caprolactone), PCL), polydioxanone (PDO), poly(glycolic acid) (PGA), poly(L-lactic acid) (PLA),poly(lactide-co-glycolide) (PLGA), poly(L-lactide) (PLLA),poly(D,L-lactide) (P(DLLA)), poly(ethylene glycol) (PEG),montmorillonite (MMT), poly(L-lactide-co-ε-caprolactone) (P(LLA-CL)),poly(E-caprolactone-co-ethyl ethylene phosphate) (P(CL-EEP)),poly[bis(p-methylphenoxy) phosphazene] (PNmPh),poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), poly(esterurethane) urea (PEUU), poly(p-dioxanone) (PPDO), polyurethane (PU),polyethylene terephthalate (PET), poly(ethylene-co-vinylacetate) (PEVA),poly(ethylene oxide) (PEO), poly(phosphazene), poly(ethylene-co-vinylalcohol), polymer nanoclay nanocomposites, poly(ethylenimine),poly(ethyleneoxide), poly vinylpyrrolidone; polystyrene (PS) andcombinations thereof. Particularly suitable polymers includepoly(lactic-co-glycolic acid), polydioxanone, polycaprolactone, andcombinations thereof.

The fibers for the fiber compositions may be of a variety of sizes asdeemed suitable by one skilled in the art for the end purpose of thenon-woven graft material. Typically, the fibers have a mean fiberdiameter of less than 5 μm, including less than 2 μm, including lessthan 1.5 μm, and including less than 1.0 μm. For example, in someembodiments, the fibers can have a mean fiber diameter ranging fromabout 10 nm to about 5 μm, more specifically from about 10 nm to about1.0 μm, more specifically still from about 20 nm to about 500 nm, andmost specifically from about 20 nm to about 400 nm. Other exemplaryranges include from about 50 nm to about 500 nm, from about 100 nm toabout 500 nm, and about 40 nm to about 200 nm.

Suitable ratios of the first fiber composition to the second fibercomposition resulting in the non-woven graft material can range fromabout 10 to 1 to about 1 to 10.

In one particularly suitable embodiment, the non-woven graft material ismade from a first non-woven fiber composition prepared frompoly(lactic-co-glycolic acid) and a second non-woven fiber compositionprepared from polydioxanone. The resultant non-woven graft material is anon-biologic tissue substitute designed to provide optimal strength,handling, and suturability, while reducing local inflammation to provideimproved wound healing and tissue regeneration. In an exemplaryembodiment the non-woven graft material can be synthesized byelectrospinning a first fiber composition including a copolymer ofglycolide and L-lactide and a second fiber composition includingpolydioxanone (100 mol %) to create an architecture that is reminiscentof native extracellular matrix. The glycolide mol % to L-lactide mol %can range from about 100 mol % glycolide to 0 mol % L-lactide to 0 mol %glycolide to about 100 mol % L-lactide. A particularly suitablenon-woven graft material includes a first fiber composition including acopolymer of glycolide and L-lactide having a glycolide mol % toL-lactide mol % ratio of 90 mol % glycolide and 10 mol % L-lactide. Thismethod of synthesis creates a material that is mechanically strong,while providing the look and feel of native tissue. The architecture ofthis non-biologic graft material furthermore supports tissue ingrowthand neoduralization with minimal inflammation.

The non-woven graft material typically can be prepared to be any of avariety of sizes, shapes and thicknesses. Wet and dry non-woven graftmaterial can suitably be cut and trimmed to any desired size and shape.In particularly suitable embodiments, the non-woven graft material has asize ranging from about 2.5 cm×2.5 cm (1 in ×1 in) to about 25.5 cm×50cm (10 in ×20 in), including for example, from about 2.5 cm×2.5 cm (1 in×1 in), from about 5.0 cm×5.0 cm (2 in ×2 in), from about 7.5 cm×7.5 cm(3 in ×3 in), and including about 12.5 cm×17.5 cm (5 in ×7 in).

The non-woven graft materials typically have a thickness ranging fromabout 0.1 mm to about 5 mm, including from about 0.3 mm to about 0.8 mm,about 0.3 mm to about 0.7 mm, and about 0.3 mm to about 0.5 mm.

The non-woven graft material is typically porous, and hasinterconnecting pores having a pore size in the range of from about 10μm² to about 10,000 μm². Particularly suitable embodiments have a poresize of less than 300 μm². It is believed that pores of this size rangecan accommodate penetration by cells and can support the growth andproliferation of cells, followed by vascularization and tissuedevelopment.

In some aspects, the non-woven graft materials can be surface-modifiedwith biomolecules such as (but not limited to) hyaluronans, collagen,laminin, fibronectin, growth factors, integrin peptides (Arg-Gly-Asp;i.e., RGD peptides), and the like, or by sodium hyaluronate and/orchitosan niacinamide ascorbate, which are believed to enhance cellmigration and proliferation, or any combination thereof. The materialcan also be impregnated with these and other bioactive agents such asdrugs, vitamins, growth factors, therapeutic peptides, and the like. Inaddition, drugs that would alleviate pain may also be incorporated intothe material.

In another aspect, the present disclosure is directed to a laminatecomprising a non-woven graft material, wherein the non-woven graftmaterial includes a first non-woven fiber composition and a secondnon-woven fiber composition.

In one embodiment, the non-woven graft material of the laminate includesa first non-woven fiber composition including poly(lactic-co-glycolicacid) and a second non-woven fiber composition including polydioxanone,as described herein.

In another embodiment, the non-woven graft material can include at leastone projection arising from a surface of the non-woven graft material.The projection is a protrusion or bulge arising from a surface of thenon-woven graft material. The projection can arise from a top surface ofthe non-woven graft material, a bottom surface of the non-woven graftmaterial, and a top surface and a bottom surface of the non-woven graftmaterial. The projection can be any desired shape such as, for example,circular, spherical, square, rectangular, diamond, star, irregular, andcombinations thereof. The projection can be any desired height asmeasured from the surface of the material to the top of the projection.In one embodiment, the projection can have a substantially uniformheight from the surface of the material. In another embodiment, theprojection can further form gradually from the surface of the materialto the highest measurable surface of the projection. In someembodiments, a surface of the non-woven graft material includes aplurality of protrusions. The plurality of protrusions can be patternedor randomly distributed on a surface of the non-woven graft material. Inanother embodiment, the method includes forming at least one indentationin a surface of the non-woven graft material. The indentation is arecess or depression in a surface of the non-woven graft material. Theindentation can in a top surface of the non-woven graft material, abottom surface of the non-woven graft material, and a top surface and abottom surface of the non-woven graft material. The indentation can beany desired shape such as, for example, circular, spherical, square,rectangular, diamond, star, irregular, and combinations thereof. Theindentation can be any desired depth as measured from the surface of thematerial to the bottom of the indentation. In one embodiment, theindentation can have a substantially uniform depth from the surface ofthe material to the deepest depth of the indentation. In anotherembodiment, the indentation can further form gradually from the surfaceof the material to the deepest depth of the indentation. In someembodiments, a surface of the non-woven graft material includes aplurality of indentations. The plurality of indentations can bepatterned or randomly distributed on a surface of the non-woven graftmaterial. In another embodiment, the non-woven graft material caninclude at least one projection arising from a surface of the non-wovengraft material and at least one indentation in the surface of thenon-woven graft material. In another embodiment, the non-woven graftmaterial can include at least one projection arising from a top surfaceof the non-woven graft material and at least one indentation in the topsurface of the non-woven graft material. In another embodiment, thenon-woven graft material can include at least one projection arisingfrom a bottom surface of the non-woven graft material and at least oneindentation in the bottom surface of the non-woven graft material. Inanother embodiment, the non-woven graft material can include at leastone projection arising from a top surface of the non-woven graftmaterial, at least one projection arising from a bottom surface of thenon-woven graft material, at least one indentation in the top surface ofthe non-woven graft material, and at least one indentation in the bottomsurface of the non-woven graft material. The plurality of indentationsand the plurality of indentations can be patterned or randomlydistributed on a surface of the non-woven graft material. Suitablemethods for forming projections and indentations include pressing,stamping, and other methods known to those skilled in the art.

Methods of Making the Non-Woven Graft Materials

In another aspect, the present disclosure is directed to methods ofpreparing the non-woven graft materials. The methods generally includepreparing aqueous solutions of the polymers described above.Particularly, fibers resulting from separate polymer solutions can becontacted together using one or more processes such as electrospinning,electrospraying, melt-blowing, spunbonding, to form the non-woven graftmaterial; and drying the non-woven graft material.

The non-woven graft material is dried to remove solvents used to preparethe aqueous polymer solutions. Drying can be done using methodsgenerally known in the art, including, without limitation, Yankee dryersand through-air dryers. Preferably, a non-compressive drying method thattends to preserve the bulk or thickness of the non-woven graft materialis employed. Suitable through-drying apparatus and through-dryingfabrics are conventional and well-known. One skilled in the art canreadily determine the optimum drying gas temperature and residence timefor a particular through-drying operation.

In one particular embodiment, a first fiber composition resulting from afirst aqueous polymer solution and a second fiber composition resultingfrom a second aqueous polymer solution are blended to form a non-wovengraft material using the electrospinning process as described above. Theelectrospinning process generally involves applying a high voltage(e.g., about 1 kV to about 100 kV, including about 3 kV to about 80 kV,depending on the configuration of the electrospinning apparatus) to apolymer fiber solution to produce a polymer jet. As the jet travels inair, the jet is elongated under repulsive electrostatic force to producenanofibers from the polymer fiber solution. The high voltage is appliedbetween the grounded surface (or oppositely charged surface) and aconducting capillary into which a polymer fiber solution is injected.The high voltage can also be applied to the solution or melt through awire if the capillary is a nonconductor such as a glass pipette.Initially the solution at the open tip of the capillary is pulled into aconical shape (the so-called “Taylor cone”) through the interplay ofelectrical force and surface tension. At a certain voltage range, a finejet of polymer fiber solution forms at the tip of the Taylor cone andshoots toward the target. Forces from the electric field accelerate andstretch the jet. This stretching, together with evaporation of solventmolecules, causes the jet diameter to become smaller. As the jetdiameter decreases, the charge density increases until electrostaticforces within the polymer overcome the cohesive forces holding the jettogether (e.g., surface tension), causing the jet to split or “splay”into a multifilament of polymer nanofibers. The fibers continue to splayuntil they reach the collector, where they are collected as nonwovennanofibers, and are optionally dried.

Suitable solvents for preparing aqueous polymer solutions include, forexample, hexafluoroisopropanol (HFIP), dichloromethane (DCM),dimethylformamide (DMF), acetone, and ethanol.

In another embodiment, the method can further include forming at leastone projection arising from a surface of the non-woven graft material,forming at least one indentation in a surface of the non-woven graftmaterial, and combinations thereof. The projection is a protrusion orbulge arising from a surface of the non-woven graft material. Theprojection can arise from a top surface of the non-woven graft material,a bottom surface of the non-woven graft material, and a top surface anda bottom surface of the non-woven graft material. The projection can beany desired shape such as, for example, circular, spherical, square,rectangular, diamond, star, irregular, and combinations thereof. Theprojection can be any desired height as measured from the surface of thematerial to the top of the projection. In one embodiment, the projectioncan have a substantially uniform height from the surface of thematerial. In another embodiment, the projection can further formgradually from the surface of the material to the highest measurablesurface of the projection. In some embodiments, a surface of thenon-woven graft material includes a plurality of protrusions. Theplurality of protrusions can be patterned or randomly distributed on asurface of the non-woven graft material. In another embodiment, themethod includes forming at least one indentation in a surface of thenon-woven graft material. The indentation is a recess or depression in asurface of the non-woven graft material. The indentation can in a topsurface of the non-woven graft material, a bottom surface of thenon-woven graft material, and a top surface and a bottom surface of thenon-woven graft material. The indentation can be any desired shape suchas, for example, circular, spherical, square, rectangular, diamond,star, irregular, and combinations thereof. The indentation can be anydesired depth as measured from the surface of the material to the bottomof the indentation. In one embodiment, the indentation can have asubstantially uniform depth from the surface of the material to thedeepest depth of the indentation. In another embodiment, the indentationcan further form gradually from the surface of the material to thedeepest depth of the indentation. In some embodiments, a surface of thenon-woven graft material includes a plurality of indentations. Theplurality of indentations can be patterned or randomly distributed on asurface of the non-woven graft material. In another embodiment, thenon-woven graft material can include at least one projection arisingfrom a surface of the non-woven graft material and at least oneindentation in the surface of the non-woven graft material. In anotherembodiment, the non-woven graft material can include at least oneprojection arising from a top surface of the non-woven graft materialand at least one indentation in the top surface of the non-woven graftmaterial. In another embodiment, the non-woven graft material caninclude at least one projection arising from a bottom surface of thenon-woven graft material and at least one indentation in the bottomsurface of the non-woven graft material. In another embodiment, thenon-woven graft material can include at least one projection arisingfrom a top surface of the non-woven graft material, at least oneprojection arising from a bottom surface of the non-woven graftmaterial, at least one indentation in the top surface of the non-wovengraft material, and at least one indentation in the bottom surface ofthe non-woven graft material. The plurality of indentations and theplurality of indentations can be patterned or randomly distributed on asurface of the non-woven graft material. Suitable methods for formingprojections and indentations include pressing, stamping, and othermethods known to those skilled in the art.

Methods of Tissue Repair

In another aspect, the present disclosure is directed to a method oftissue repair in an individual in need thereof. The method includes:applying a non-woven graft material to a surgical field, wherein thenon-woven graft material comprises a first fiber composition and asecond fiber composition. The method is particularly suitable forrepairing tissues such as, for example, dura mater, pericardium, smallintestinal submucosa, dermis, epidermis, tendon, trachea, heart valveleaflet, gastrointestinal tract, and cardiac tissue. Suitable tissuerepair procedures include, for example, neurosurgeries such as duramater repair, skin grafts, tracheal repair, gastrointestinal tractrepair (e.g., abdominal hernia repair, ulcer repair), cardiac defectrepair, head and neck surgeries, application to bone fractures, and burnrepair.

Suitably, the non-woven graft material includes a first fibercomposition, wherein the first fiber composition includes a polymerselected from polycaprolactone (poly(ε-caprolactone), PCL),polydioxanone (PDO), poly (glycolic acid) (PGA), poly(L-lactic acid)(PLA), poly(lactide-co-glycolide) (PLGA), poly(L-lactide) (PLLA),poly(D,L-lactide) (P(DLLA)), poly(ethylene glycol) (PEG),montmorillonite (MMT), poly(L-lactide-co-ε-caprolactone) (P(LLA-CL)),poly(ε-caprolactone-co-ethyl ethylene phosphate) (P(CL-EEP)),poly[bis(p-methylphenoxy) phosphazene] (PNmPh),poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), poly(esterurethane) urea (PEUU), poly(p-dioxanone) (PPDO), polyurethane (PU),polyethylene terephthalate (PET), poly(ethylene-co-vinylacetate) (PEVA),poly(ethylene oxide) (PEO), poly(phosphazene), poly(ethylene-co-vinylalcohol), polymer nanoclay nanocomposites, poly(ethylenimine),poly(ethyleneoxide), poly vinylpyrrolidone; polystyrene (PS) andcombinations thereof. Particularly suitable polymers includepoly(lactic-co-glycolic acid), polydioxanone, polycaprolactone, andcombinations thereof.

Suitably, the non-woven graft material includes a second fibercomposition, wherein the second fiber composition includes a polymerselected from polycaprolactone (poly(ε-caprolactone), PCL),polydioxanone (PDO), poly (glycolic acid) (PGA), poly(L-lactic acid)(PLA), poly(lactide-co-glycolide) (PLGA), poly(L-lactide) (PLLA),poly(D,L-lactide) (P(DLLA)), poly(ethylene glycol) (PEG),montmorillonite (MMT), poly(L-lactide-co-ε-caprolactone) (P(LLA-CL)),poly(ε-caprolactone-co-ethyl ethylene phosphate) (P(CL-EEP)),poly[bis(p-methylphenoxy) phosphazene] (PNmPh),poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHB V), poly(esterurethane) urea (PEUU), poly(p-dioxanone) (PPDO), polyurethane (PU),polyethylene terephthalate (PET), poly(ethylene-co-vinylacetate) (PEVA),poly(ethylene oxide) (PEO), poly(phosphazene), poly(ethylene-co-vinylalcohol), polymer nanoclay nanocomposites, poly(ethylenimine),poly(ethyleneoxide), poly vinylpyrrolidone; polystyrene (PS) andcombinations thereof. Particularly suitable polymers includepoly(lactic-co-glycolic acid), polydioxanone, polycaprolactone, andcombinations thereof.

In a particularly suitable embodiment, the non-woven graft materialincludes a first fiber composition comprising poly(lactic-co-glycolicacid) and a second fiber composition comprising polydioxanone.

As used herein, “individual in need thereof” refers to an individualhaving a tissue defect, tissue damage, tissue that is missing due todamage or removal, and tissue damaged by incision. The methods areparticularly suitable for use with an individual or subset ofindividuals having dura defects requiring repair of the dura mater.Individuals having dura defects can be those having a perforation in thedura mater, those having dura mater removed, those having damaged duramater, and those having dura mater with a surgical incision.

The individual in need thereof can be an adult individual, a child, anda pediatric individual. Particularly suitable individuals can be ahuman. Other particularly suitable individuals can be animals such asprimates, pigs, dogs, cats, rabbits, rodents (e.g., mice and rats), andthe like.

In some embodiments, the non-woven graft material is secured to thesurgical field, such as by suturing the non-woven graft material to thesurgical field. In other embodiments, the non-woven graft material issecured to the surgical field, such as by a surgical adhesive.

EXAMPLES Example 1

In this Example, the performance of a gold-standard xenogenic collagengraft material was compared to an exemplary embodiment of the non-wovengraft material of the present disclosure.

Materials and Methods

Study Design

Ten female New Zealand White rabbits (5.0-5.5 months, Western OregonRabbit Company, Philomath, OR) were randomized into two groups of fiveanimals each (n=5). Group I served as the positive control as allanimals underwent bilateral craniotomy and dural resection followed bybilateral surgical repair of the induced dural defects utilizing acollagen graft material (Stryker, Inc. Kalamazoo, MI). Group II servedas an experimental group as all animals underwent bilateral craniotomyand dural resection followed by bilateral surgical repair of the induceddural defects utilizing the fully resorbable non-biologic non-wovengraft material. All animals underwent daily/weekly behavioral assessmentand examination for signs of neurotoxicity, neurological sequelae, CSPleakage, and infection. Four weeks post-operatively all animals wereeuthanized and repair sites, including proximal skull and underlyingcortical tissue, were explanted for histological and histopathologicalanalysis. All animal procedures were performed in strict accordance withguidelines set by the Animal Welfare Act (AWA), the Association forAssessment and Accreditation of Laboratory Animal Care (AAALAC), andInstitutional Animal Care and Use Committee (IACUC) of the University ofUtah.

Surgical Procedure: Bilateral Craniotomy

Prior to surgery, all animals were administered butorphanol,acepromazine, cefazolin, and dexamethasone, as well as a transdermalfentanyl patch for prophylactic analgesia. All animals were anesthetizedvia ketamine and diazepam, administered intravenously viacatheterization of the marginal ear vein, and maintained through theduration of the surgery via isoflurane. The cranium was then asepticallyprepared and sterilized from the frontal ridge to the occiput. All hairwas removed and the surgical site was prepared with povidone iodine andisopropyl alcohol. A 6-cm midline sagittal incision was then madeextending through the scalp and the underlying periosteum. Theperiosteum was then elevated and retracted. Bilateral bone flaps werethen created on either side of the skull utilizing a high-speedneurosurgical drill fitted with a matchstick bit. Resulting bone flapsmeasuring approximately 10 mm×12 mm were then elevated and removedexposing the underlying dura mater. The dura mater was incisedbilaterally utilizing a micro-dissection blade and two circular duraldefects each approximately 8 mm×10 mm were created undermicrodissection.

Surgical Procedure: Dural Repair

Induced dural defects were subsequently repaired with either thecollagen graft material or the fully resorbable non-biologic non-wovengraft material (FIGS. 1A & 1B). The collagen graft material is abiologic, xenogenic graft material composed of type I collagen derivedfrom bovine Achilles tendon. The collagen graft material is highlycrosslinked resulting in a firm, woven, suturable implant materialsuitable for use in dural repair. The collagen graft material wasprovided sterile and stored at room temperature prior to use. Thenon-woven graft material is a fully-resorbable non-biologic graftmaterial composed of electrospun poly(lactic-co-glycolic acid) andpolydioxanone. It possesses a unique non-woven architecture resulting ina compliant, flexible, and suturable implant material indicated for usein the repair of the duramater. The fully resorbable non-biologicnon-woven graft material was provided sterile and stored at roomtemperature prior to use.

Prior to implantation, both graft materials were hydrated in sterilesaline according to their respective instructions for use. Hydratedgraft materials were then placed on the surgical field and trimmed tofit each dural defect. The size and shape of the graft material wasselected to achieve at least a 2 mm overlap with the adjacent dura materaround the circumference of the defect. Hydrated grafts were then drapedonto the dural defect to maximize contact between the graft material andthe underlying dura and promote watertight closure. Graft materials werethen secured to the native dura utilizing four interrupted, non-tensionsutures (7-0 PDS) spaced equidistant around the circumference of thedefect. Graft materials were implanted such that each animal receivedeither two collagen graft material implants (n=5 animals) or twonon-woven graft material implants (n=5 animals). Following repair ofinduced dural defects, each surgical site was irrigated and closed intwo layers (periosteum/muscle, skin). Excised bone flaps were notreplaced during closure.

Following surgery all animals were recovered prior to reintroductioninto the general housing facility. Butorphanol was administered as apost-surgical analgesic in addition to the fentanyl transdermal patch.Post-operatively all animals were observed daily and evaluated weeklyfor behavioral signs of neurotoxicity (posture, pupillary light reflex,limb placement, proprioception reflex, corneal reflex, gait),indications of CSP leakage, and change in body weight.

Tissue Harvesting/CSP Evaluation

All animals were humanely euthanized 4 weeks post-operatively. CSP wascollected for physiochemical analysis by inserting a needle into thecisterna magna and aspirating 1-2 ml of fluid which was then placed incold-storage. Following CSP collection, the skull, brain, and implantsites were excised en bloc and fixed in neutral buffered formalin.Draining lymph nodes were similarly explanted and fixed in neutralbuffered formalin. CSP fluid was sent Logan Regional Hospital (Logan,UT) for physiochemical analysis. CSP was analyzed for cellular content(white blood cells, neutrophils, lymphocytes, monocytes/macrophages,eosinophils, basophils, lining cells, red blood cells) as well asglucose and protein levels.

Histological/Histopathological Analysis

Explanted skulls and peripheral lymph nodes were embedded in epoxyresin, blocked, and sectioned. Sections of the implant site (includingneodural tissue and adjacent skull/brain) were stained with Luxol FastBlue and Hematoxylin & Eosin (H&E) to visualize and evaluate the generalhealth of neodural tissue, cortical tissue, and myelin. Sections of theimplant site were also immunostained for Glial Fibrillary Acidic Protein(GFAP) to visualize local glial cells/astrocytes and evaluate theinflammatory response at the implant site. Sections of the lymph nodeswere stained only with Hematoxylin & Eosin (H&E). Representativephotomicrographs were then obtained utilizing light microscopy under a40× optical objective and a Nanozoomer automated slide scanner providedby the Hope Center, Washington University School of Medicine.

The local tissue response to implanted dura substitute materials wasquantified via microscopic scoring of neovascularization,vascularization of the tissue within the implant site, fibrosis,adhesions of the implant to the pia mater, and neoduralization. Fibrouscapsule thickness (in μm) was averaged between three measurements ineach implant site. If the presence of implant was not well defined, thethickness of fibrous tissue at the implant site was reported.Inflammation at the implant site was quantified by microscopicallyscoring the degree of infiltration of polymorphonuclear cells,lymphocytes, plasma cells, eosinophils, macrophages, and multinucleatedgiant cells into the implant field. Necrosis was scored as the severityof nuclear cellular debris from inflammatory cell death.

Results

Intraoperative/Postoperative Performance of Dura Substitute Materials

Both collagen biologic and non-biologic graft materials weresuccessfully utilized to repair induced bilateral dural defects createdin female New Zealand White rabbits. Intraoperative observationsdemonstrated that both commercially-available collagen-based grafts andfully-resorbable synthetic non-woven grafts possessed suitableproperties for effective dural repair. Upon surgical implantation thenon-woven graft material implants were noted to be less thick and moreflexible/compliant than the collagen-based graft implants. The non-wovengraft material implants were also observed to better conform tounderlying native dura and were more easily sutured in place compared tothe collagen-based graft implants.

Post-operatively all animals survived to the terminal time point and allanimals exhibited normal behavior, neurological function and generalhealth. Regular examination of the implant site confirmed that 0/10implant sites containing the collagen-based graft implants and 0/10implant sites containing The non-woven graft material exhibited signs ofCSP leakage or focal implant site infection during the course of thestudy. Post-mortem examination of the repair sites further confirmed theabsence of CSP leaks and pseudomeningocele in all animals on study.Post-operative observation demonstrated that both the non-woven graftmaterial and the collagen-based graft implants were efficacious inrepairing dural defects and preventing CSP leakage.

Analysis of Cerebrospinal Fluid/Sentinel Lymph Nodes

Cellular and physiochemical analysis of CSP collected from animalsundergoing dural repair utilizing the collagen-based graft and thenon-woven graft material was conducted in order to identify potentialsigns of neurotoxicity, inflammation, and/or infection resulting fromimplant materials. Complete blood counts and protein analysis conductedon collected CSP appeared normal in all animals implanted with both thecollagen-based graft and the non-woven graft materials. Negativefindings in CSP analysis suggest that neither implant material inducedneurotoxic or inflammatory responses in regional cortical tissue.Histological analysis of sentinel lymph nodes was conducted in order tofurther examine the inflammatory and foreign body response to the duralsubstitute implants. Animals implanted with both the collagen-basedgraft and the non-woven graft materials exhibited normal appearing lymphnodes upon H&E staining suggesting no regional inflammatory or foreignbody response to the grafts.

Histological/Histopathological Analysis of Implant Sites

Histological and histopathological analysis of surgical repair sites wasconducted to qualitatively and quantitatively evaluate the efficacy ofvarious dura substitute materials and the tissue/inflammatory responseto the implanted grafts. Qualitative analysis of representative sectionsof defect sites repaired with either the collagen-based graft and thenon-woven graft materials demonstrate significant differences in theefficacy of the implanted material (FIGS. 2A-2D). Coronal sectionsobtained from defect sites repaired with the collagen-based graftmaterial demonstrated poor cellular infiltration and incorporation intothe graft material. Sections further demonstrated frequent fibrousadhesions or connective tissue bridging the implanted the collagen-basedgraft material and the underlying cortical tissue. Qualitativeobservations further demonstrated frequent incomplete neoduralizationacross the cortical surface of the collagen-based graft material. Incomparison, qualitative analysis of representative histological sectionsobtained from defect sites repaired with the fully-resorbable non-wovengraft material demonstrated increased cellular infiltration and lowerincidence of fibrous cortical adhesions. Coronal sections furtherdemonstrated more complete neoduralization across the cortical surfaceof the non-woven graft material. Noted differences in tissue response tothe implanted materials further related to the state of graft resorptionat the time of explantation. At 4 weeks post-operatively, thecollagen-based graft material demonstrated minimal cellular infiltrationand resorption, while the non-woven graft material demonstrated markedcellular infiltration and resorption (FIGS. 2A-2D).

Quantitative scoring of histologic sections provided additionalcomparison of the tissue level reaction to both dura substitute devices.Microscopic scoring of histopathological examinations of the implantsite revealed significant differences in the inflammatory andtissue-level responses to the non-woven graft material, as compared tothe collagen-based graft material (FIGS. 3A & 3B and Table 1). Thenon-woven graft materials were observed to recruit a reduced number ofinflammatory cells (e.g. monocytes and lymphocytes) compared to thecollagen-based graft materials (see Table 1). The non-woven graftmaterials also exhibited less fibrosis and lower fibrous capsulethicknesses compared to the collagen-based graft material.Histopathological scoring of inflammation and tissue response furtherindicated that the non-woven graft material exhibited a lowerinflammatory response, and was therefore classified as non-irritant,compared to the collagen-based graft material.

TABLE 1 Histopathological Evaluation Graft Material Non-woven Collagen-Graft based Material Graft Material Inflammation Polymorphonuclear 0 0.8cells^(a) Lymphoytes^(a) 0 0.9 Plasma cells^(a) 0 0.3 Eosinophils^(a) 00 Mast cells^(a) 0 0 Macrophages^(a) 0.8 0.8 Multinucleated giant 0.9 0cells^(a) Necrosis^(b) 0 0 Tissue Neovascularization^(c) 1.0 1.0Response Implant 1.5 0.4 vascularization^(d) Neoduralization^(e) 3.6 1.3Fibrosis^(f) 2.3 3.1 Pia mater adhesions^(e) 0.9 2.2 ^(a)Scored from 0(absent)-4 (packed). ^(b)Scored from 0 (absent)-4 (severe). ^(c)Scoredfrom 0 (absent)-4 (extensive capillaries supported by fibroblasts).^(d)Scored from 0 (absent)-5 (>75% of implant field). ^(e)Scored from 0(absent)-5 (100% of implant field). ^(f)Scored from 0 (no fibrouscapsule)-4 (fibrous capsule > 300 um thick).

The results presented herein offer a comparative analysis of thenon-woven graft material and the collagen-based graft material in abilateral rabbit duraplasty model. Both materials demonstrated effectiverepair of induced dural defects and prevention of CSP leakage withoutdamaging proximal neural tissue. This functional comparison demonstratesequivalent performance of the non-woven graft material withgold-standard collagen-matrices widely used in contemporaryneurosurgical clinics. Histopathological analysis of the implant site 4weeks post-operatively revealed, however, that the performance of thenon-woven graft material and the collagen-based graft material were notequivalent when considering local inflammatory and tissue-levelresponses elicited at the site of implantation. The non-woven graftmaterial exhibited distinct advantages in local tissue responseincluding reduced fibrosis/fibrous capsule formation and decreasedcortical adhesions compared to the collagen-based graft material (FIGS.3A-3B). Furthermore, the non-woven graft material induced greaterneoduralization than the collagen-based graft material at the implantsite, and in some cases the non-woven graft material supported completeneoduralization of the defect by the time of explantation (FIG. 3C).

The difference in tissue response to the non-woven graft material andthe collagen-based graft material is likely influenced by differences inthe composition of the implants and, specifically, differences in theresorbable nature of the materials. The collagen-based graft materialdid not appear to undergo significant resorption 4 weeks afterimplantation, but rather was associated with minimal cellular/tissueinfiltration and significant fibrous capsule around the acellular,crosslinked collagen material. Thus, although the collagen-based graftmaterial is composed of biologically-derived animal-based collagen, thebiological response to the implanted material is unlike what may beexpected of native protein. The collagen-based graft material, despiteits biologic composition, exhibits an in vivo response significantlydivergent to that of native or fresh tissue.

Alternatively, the non-woven graft material implant demonstrated modestresorption in parallel with increased cellular infiltration of thematerial. Particularly, resorbing elements of the non-woven graftmaterial implant were observed to be localized within macrophages thathad infiltrated the implant site. This observation confirms theresorbable and transient nature of the non-woven graft material. Thesynthetic electrospun material utilized in the construction of thenon-woven graft material provided an environment in which cells couldmigrate and which could be broken down to allow subsequent remodeling ofthe tissue. Fully-resorbable constructs such as the non-woven graftmaterial may possess multiple advantages over long-term or permanentimplants in that the material serves as an acute barrier and scaffoldfor new tissue formation yet resorbs following tissue regenerationprecluding undue chronic reactions to the implanted material.Furthermore, the lack of animal-derived, xenogenic, or allogenicconstituents may effectively reduce the incidence of allergic orinflammatory responses to the implanted dura substitute materialcommonly associated with existing biologic graft materials.

The lack of resorption of the implanted the collagen-based graftmaterial is likely an effect of the post-processing utilized in theconstruction of the biologic material. The crosslinking of bovinecollagen required to provide the mechanical strength necessary forintraoperative use and suturability simultaneously affected the biologicand structural elements of the material. As demonstrated in thisExample, fully-resorbable synthetic dura substitutes can provideadequate mechanical strength for suturability, optimal handling andcompliance, as well as reliable resorption that encourages tissueremodeling in the form of neoduralization. the non-woven graft materialis unique, however, in that the non-biologic dura substitute alsoexhibits reduced inflammation, decreased fibrosis, and fewer adhesionsto the pia mater than gold-standard biologic dura substitutes presentlyin use in neurosurgical clinics. The non-woven architecture, created byelectrospinning, may be attributed with an improved tissue response, ascompared to alternative synthetic dura substitutes. Furthermore, thismechanism of synthesis provides a material with superior handling anddrapability as compared to alternatives with reduced compliance. Thenon-woven graft materials (e.g., the non-woven graft material) of thepresent disclosure thereby offer a unique and attractive option in duralrepair procedures that provides ease of handling, efficacy, andbiocompatibility, ultimately leading to improved dural repair.

The non-woven graft materials of the present disclosure providefully-resorbable, non-biologic dura substitutes that offer a uniquecombination of mechanical strength for suturability and compliance forease of handling. The non-woven architecture of the materials permitscellular infiltration and supports full resorption of the implantmaterial while encouraging regeneration of native dura. The materialseffectively closed dura defects equivalent to a gold-standard biologicdura substitute (the collagen-based graft material) and induced asuperior local tissue response characterized by decreased inflammationand increased neoduralization. The non-woven graft materials therebyoffer significant advantages over existing dura substitutes that maylead to improved clinical outcomes in multiple neurosurgical settings.

Example 2

In this Example, the physical properties of the non-woven mesh weredetermined by direct measurements of mesh fiber, pore size, mass, anddimensions.

Test articles were cut into four portions of approximately 1 cm² each.Excised portions were attached to a standard 12 mm SEM stub using doublesided carbon tape. Two portions were positioned in a “dimple up”orientation and two portions were positioned in a “dimple down”orientation. Samples were coated with −20 Å of gold using a Denton DeskV sputter coater. Physical properties analyzed were average pore size,average fiber diameter, average thickness, side dimension, mass, and“areal density” (g/m²). Dimensional data was collected by recording aseries of secondary electron micrographs from each sample using a TESCANVega 3 scanning electron microscope. A magnification level of 2 kx wasspecified for data collection. Images were also collected at 500×magnification. Physical properties were measured directly on themicrographs using calibrated software embedded in the TESCAN operatingsystem. The number of properties recorded per micrograph were 30 fibersper image and 20 pores per image. Fiber and pore locations were randomlyselected. Mean thickness was determined by averaging five measurementsfrom a 100× cross section field of view. Side dimension was measuredwith a calibrated ruler traceable to NIST standards. Mass was determinedby weighing samples on a calibrated analytical balance before cutting.

Example 3

In this Example, the non-destructive testing was conducted on non-wovenmaterial of the disclosure.

Mass was determined by weighing the sample on a balance. Size wasmeasured to include the length and width of the material usingcalibrated calipers. Area (cm²) was calculated. “Areal density” (g/m²)was calculated using mass and size measurements.

Example 4

In this Example, the tensile strength on non-woven material of thedisclosure was analyzed.

Specifically the tensile strength of 1 inch×3 inch strips prepared froma 3 inch×3 inch non-woven graft material sample at break and %elongation at break was performed using an Instron Tester. A 1 inch×3inch strip was placed into the grips of the Instron Tester. Location ofthe break, gauge length, grip separation speed, sample and specificationidentification, specimen size parameters and preconditioning parameterswere noted. Tensile strength was measured in Newtons (N) and the %elongation at break was measured in %.

Example 5

In this Example, the “suture pull-out” or the force required to pull outa suture from non-woven material of the disclosure was analyzed.

The force required to pull out a suture from non-woven material of thedisclosure was analyzed using an Instron Tester on 1 inch×3 inch stripsprepared from a 3 inch×3 inch non-woven graft material sample. Stripswere soaked for 2 hours at room temperature in de-ionized water. Gaugelength was set to 100.8 mm and the grip separation speed was set at 75mm/minute. A 2-0 polypropylene monofilament suture was threaded throughthe center of the strip approximately 7.5 mm from the upper edge of thesample. Suture ends were clamped. Tearing of the sample was noted anddata excluded suture breakage. The maximum pull-out force was measuredin Newtons (N).

This materials and methods disclosed herein provide substitute materialsfor tissue repair. In particular, the materials and methods disclosedherein provide a non-biological substitute for tissue repair.

What is claimed is:
 1. A bioabsorbable non-woven graft material forfacilitating regeneration of tissue, the bioabsorbable non-woven graftmaterial comprising: a single layer non-woven electrospun polymericscaffold configured to facilitate tissue growth within the single layernon-woven electrospun polymeric scaffold wherein the single layernon-woven electrospun polymeric scaffold is configured to be bioabsorbedwhereby the facilitated tissue growth remains after the single layernon-woven electrospun polymeric scaffold is bioabsorbed, the singlelayer non-woven electrospun polymeric scaffold comprising: a firstelectrospun non-woven fiber composition, wherein the first electrospunnon-woven fiber composition comprises a first polymer comprisingglycolic acid; and a second electrospun non-woven fiber composition,wherein the second electrospun non-woven fiber composition comprises asecond polymer comprising caprolactone, wherein the first electrospunnon-woven fiber composition and the second electrospun non-woven fibercomposition comprise different polymers, wherein the first electrospunnon-woven fiber composition and the second electrospun non-woven fibercomposition are electrospun to form throughout the single layernon-woven electrospun polymeric scaffold of the bioabsorbable non-wovengraft material to create an architecture resembling a nativeextracellular matrix, wherein the bioabsorbable non-woven graft materialfurther comprises a first region and a second region, wherein thebioabsorbable non-woven graft material further comprises a plurality ofpores formed among the first electrospun non-woven fiber composition andthe second electrospun non-woven fiber composition, wherein a density ofthe first region is less than a density of the second region, whereinthe single non-woven electrospun polymeric scaffold is sufficientlyflexible for applying the bioabsorbable non-woven graft material totissue, the non-woven electrospun polymeric scaffold has sufficientmechanical strength for the bioabsorbable non-woven graft material to besuturable, and the non-woven electrospun polymeric scaffold hassufficient mechanical strength for the bioabsorbable non-woven graftmaterial to be trimmable, wherein the bioabsorbable non-woven graftmaterial is configured to be used in conjunction with one or moresutures for attaching the bioabsorbable non-woven graft material to thetissue, wherein the bioabsorbable non-woven graft material is configuredto facilitate regeneration of the tissue, wherein the bioabsorbablenon-woven graft material does not comprise more than one non-wovenelectrospun polymeric scaffold.
 2. The bioabsorbable non-woven graftmaterial of claim 1, wherein the tissue comprises tendon, and thebioabsorbable non-woven graft material is configured to repair oraugment at least the tendon.
 3. The bioabsorbable non-woven graftmaterial of claim 1, wherein the bioabsorbable non-woven graft materialcomprises one or more hollow hole depression areas.
 4. The bioabsorbablenon-woven graft material of claim 3, wherein the bioabsorbable non-wovengraft material is configured to receive the one or more sutures in thebioabsorbable non-woven graft material through the one or moredepression areas.
 5. The bioabsorbable non-woven graft material of claim1, wherein the bioabsorbable non-woven graft material comprises astructure of fibers that are interlaid in an arrangement to create thearchitecture resembling the native extracellular matrix.
 6. Thebioabsorbable non-woven graft material of claim 1, wherein thebioabsorbable non-woven graft material comprises a suture pull-outstrength, the suture pull-out strength ranging from 1 Newtons to about 5Newtons of force required for the one or more sutures to be torn frombioabsorbable non-woven graft material.
 7. The bioabsorbable non-wovengraft material of claim 1, wherein the bioabsorbable non-woven graftmaterial comprises one or more pores to promote cell infiltration. 8.The bioabsorbable non-woven graft material of claim 1, wherein thebioabsorbable non-woven graft material comprises interconnecting pores.9. The bioabsorbable non-woven graft material of claim 1, thebioabsorbable non-woven graft material comprising a surface pattern. 10.The bioabsorbable non-woven graft material of claim 9, wherein thesurface pattern comprises a repeating non-random pattern.
 11. Thebioabsorbable non-woven graft material of claim 1, wherein the firstelectrospun non-woven fiber composition and the second electrospunnon-woven fiber composition are uniformly distributed throughout thebioabsorbable non-woven graft material.
 12. The bioabsorbable non-wovengraft material of claim 1, wherein the first electrospun non-woven fibercomposition and the second electrospun non-woven fiber compositioncomprises an average diameter not greater than 5,000 nanometers.
 13. Abioabsorbable non-woven graft material for facilitating regeneration oftissue, the bioabsorbable non-woven graft material comprising: a singlelayer non-woven electrospun polymeric scaffold configured to facilitatetissue growth within the single layer non-woven electrospun polymericscaffold wherein the single layer non-woven electrospun polymericscaffold is configured to be bioabsorbed whereby the facilitated tissuegrowth remains after the single layer non-woven electrospun polymericscaffold is bioabsorbed, the single layer non-woven electrospunpolymeric scaffold comprising: a first electrospun non-woven fibercomposition, wherein the first electrospun non-woven fiber compositioncomprises a first polymer comprising polydioxanone; and a secondelectrospun non-woven fiber composition, wherein the second electrospunnon-woven fiber composition comprises a second polymer, wherein thefirst electrospun non-woven fiber composition and the second electrospunnon-woven fiber composition comprise different polymers, wherein thefirst electrospun non-woven fiber composition and the second electrospunnon-woven fiber composition are electrospun to form the single layernon-woven electrospun polymeric scaffold of the bioabsorbable non-wovengraft material to create an architecture resembling a nativeextracellular matrix, wherein the bioabsorbable non-woven graft materialfurther comprises a first region and a second region, wherein thebioabsorbable non-woven graft material further comprises a plurality ofpores formed among the first electrospun non-woven fiber composition andthe second electrospun non-woven fiber composition, wherein a density ofthe first region is less than a density of the second region, whereinthe single non-woven electrospun polymeric scaffold is sufficientlyflexible for applying the bioabsorbable non-woven graft material totissue and the non-woven electrospun polymeric scaffold has sufficientmechanical strength for the bioabsorbable non-woven graft material to betrimmable, wherein the bioabsorbable non-woven graft material isconfigured to be attached to the tissue, and wherein the bioabsorbablenon-woven graft material is configured to facilitate regeneration of thetissue, wherein the bioabsorbable non-woven graft material does notcomprise more than one non-woven electrospun polymeric scaffold.
 14. Thebioabsorbable non-woven graft material of claim 13, wherein the secondpolymer comprises poly(lactic-co-glycolic acid).
 15. The bioabsorbablenon-woven graft material of claim 14, wherein the tissue comprises oneor more of dura mater, pericardium, small intestinal submucosa, dermis,epidermis, tendon, trachea, heart valve leaflet, gastrointestinal tract,and cardiac tissue.
 16. The bioabsorbable non-woven graft material ofclaim 14, wherein the bioabsorbable non-woven graft material isconfigured to be attached to the tissue using one or more sutures. 17.The bioabsorbable non-woven graft material of claim 16, wherein thebioabsorbable non-woven graft material comprises one or more hollow holedepression areas.
 18. The bioabsorbable non-woven graft material ofclaim 17, wherein the bioabsorbable non-woven graft material isconfigured to receive the one or more sutures in the bioabsorbablenon-woven graft material through the depression area.
 19. Thebioabsorbable non-woven graft material of claim 16, wherein thebioabsorbable non-woven graft material comprises a suture pull-outstrength, the suture pull-out strength ranging from 1 Newtons to about 5Newtons of force required for the one or more sutures to be torn frombioabsorbable non-woven graft material.
 20. The bioabsorbable non-wovengraft material of claim 14, wherein the bioabsorbable non-woven graftmaterial comprises a structure of fibers that are interlaid in anarrangement to create the architecture resembling the nativeextracellular matrix.
 21. The bioabsorbable non-woven graft material ofclaim 14, wherein the bioabsorbable non-woven graft material comprisesone or more pores to promote cell infiltration.
 22. The bioabsorbablenon-woven graft material of claim 14, wherein the bioabsorbablenon-woven graft material comprises interconnecting pores.
 23. Thebioabsorbable non-woven graft material of claim 14, the bioabsorbablenon-woven graft material comprising a surface pattern.
 24. Thebioabsorbable non-woven graft material of claim 23, wherein the surfacepattern comprises a repeating non-random pattern.
 25. The bioabsorbablenon-woven graft material of claim 14, wherein the first electrospunnon-woven fiber composition and the second electrospun non-woven fibercomposition are uniformly distributed throughout the bioabsorbablenon-woven graft material.
 26. The bioabsorbable non-woven graft materialof claim 14, wherein the first electrospun non-woven fiber compositionand the second electrospun non-woven fiber composition comprises anaverage diameter not greater than 5,000 nanometers.
 27. A bioabsorbablenon-woven graft material for facilitating regeneration of tissue, thebioabsorbable non-woven graft material comprising: a single layernon-woven electrospun polymeric scaffold configured to facilitate tissuegrowth within the single layer non-woven electrospun polymeric scaffoldwherein the single layer non-woven electrospun polymeric scaffold isconfigured to be bioabsorbed whereby the facilitated tissue growthremains after the single layer non-woven electrospun polymeric scaffoldis bioabsorbed, the single layer non-woven electrospun polymericscaffold comprising: a first electrospun non-woven fiber composition,wherein the first electrospun non-woven fiber composition comprises afirst polymer comprising glycolic acid; and a second electrospunnon-woven fiber composition, wherein the second electrospun non-wovenfiber composition comprises a second polymer comprising caprolactone,wherein the first electrospun non-woven fiber composition and the secondelectrospun non-woven fiber composition comprise different polymers,wherein the first electrospun non-woven fiber composition and the secondelectrospun non-woven fiber composition are electrospun to form thesingle layer non-woven electrospun polymeric scaffold of thebioabsorbable non-woven graft material to create an architectureresembling a native extracellular matrix, wherein the bioabsorbablenon-woven graft material is configured to be attached to the tissue, andwherein the bioabsorbable non-woven graft material is configured tofacilitate regeneration of the tissue, wherein the bioabsorbablenon-woven graft material further comprises a first region and a secondregion, wherein the bioabsorbable non-woven graft material furthercomprises a plurality of pores formed among the first electrospunnon-woven fiber composition and the second electrospun non-woven fibercomposition, wherein a density of the first region is less than adensity of the second region, wherein the single non-woven electrospunpolymeric scaffold is sufficiently flexible for applying thebioabsorbable non-woven graft material to tissue, the non-wovenelectrospun polymeric scaffold has sufficient mechanical strength forthe bioabsorbable non-woven graft material to be suturable, and thenon-woven electrospun polymeric scaffold has sufficient mechanicalstrength for the bioabsorbable non-woven graft material to be trimmable,wherein the bioabsorbable non-woven graft material comprises a suturepull-out strength, the suture pull-out strength ranging from 1 Newton toabout 5 Newtons of force required for a suture to be torn frombioabsorbable non-woven graft material, wherein the bioabsorbablenon-woven graft material does not comprise more than one non-wovenelectrospun polymeric scaffold.
 28. The bioabsorbable non-woven graftmaterial of claim 27, wherein the tissue comprises one or more of duramater, pericardium, small intestinal submucosa, dermis, epidermis,tendon, trachea, heart valve leaflet, gastrointestinal tract, andcardiac tissue.
 29. The bioabsorbable non-woven graft material of claim27, wherein the bioabsorbable non-woven graft material is configured tobe attached to the tissue using one or more sutures.
 30. Thebioabsorbable non-woven graft material of claim 28, wherein thebioabsorbable non-woven graft material comprises one or more hollow holedepression areas.
 31. The bioabsorbable non-woven graft material ofclaim 30, wherein the bioabsorbable non-woven graft material isconfigured to receive the one or more sutures in the bioabsorbablenon-woven graft material through the one or more depression areas. 32.The bioabsorbable non-woven graft material of claim 27, wherein thebioabsorbable non-woven graft material is configured to be attached tothe tissue using one or more adhesives.
 33. The bioabsorbable non-wovengraft material of claim 27, wherein the bioabsorbable non-woven graftmaterial comprises a structure of fibers that are interlaid in anarrangement to create the architecture resembling the nativeextracellular matrix.
 34. The bioabsorbable non-woven graft material ofclaim 27, wherein the bioabsorbable non-woven graft material comprisesone or more pores to promote cell infiltration.
 35. The bioabsorbablenon-woven graft material of claim 27, wherein the bioabsorbablenon-woven graft material comprises interconnecting pores.
 36. Thebioabsorbable non-woven graft material of claim 27, the bioabsorbablenon-woven graft material comprising a surface pattern.
 37. Thebioabsorbable non-woven graft material of claim 36, wherein the surfacepattern comprises a repeating non-random pattern.
 38. The bioabsorbablenon-woven graft material of claim 27, wherein the first electrospunnon-woven fiber composition and the second electrospun non-woven fibercomposition are uniformly distributed throughout the bioabsorbablenon-woven graft material.
 39. The bioabsorbable non-woven graft materialof claim 27, wherein the first electrospun non-woven fiber compositionand the second electrospun non-woven fiber composition comprises anaverage diameter not greater than 5,000 nanometers.
 40. Thebioabsorbable non-woven graft material of claim 1, wherein the firstregion is a top surface and the second region is a bottom surface. 41.The bioabsorbable non-woven graft material of claim 1, wherein the firstregion is a bottom surface and the second region is a top surface. 42.The bioabsorbable non-woven graft material of claim 13, wherein thefirst region is a top surface and the second region is a bottom surface.43. The bioabsorbable non-woven graft material of claim 13, wherein thefirst region is a bottom surface and the second region is a top surface.44. The bioabsorbable non-woven graft material of claim 27, wherein thefirst region is a top surface and the second region is a bottom surface.45. The bioabsorbable non-woven graft material of claim 27, wherein thefirst region is a bottom surface and the second region is a top surface.46. The bioabsorbable non-woven graft material of claim 1, wherein thebioabsorbable non-woven graft material further comprises a top surfaceand a bottom surface, wherein the top surface or bottom surfacecomprises a plurality of protrusions.
 47. The bioabsorbable non-wovengraft material of claim 13, wherein the bioabsorbable non-woven graftmaterial further comprises a top surface and a bottom surface, whereinthe top surface or bottom surface comprises a plurality of protrusions.48. The bioabsorbable non-woven graft material of claim 27, wherein thebioabsorbable non-woven graft material further comprises a top surfaceand a bottom surface, wherein the top surface or bottom surfacecomprises a plurality of protrusions.